1. Field of the Invention
The present invention relates to an on-vehicle navigation apparatus, and more particularly to an on-vehicle navigation apparatus which functions to collect information of the locus of a moving vehicle on the basis of map information and the location of the vehicle, and to display the information on a display device (hereinafter referred to as "display").
2. Description of Background Information
On-vehicle navigation apparatuses are put into practiccal use, which generally are structured such that map information is stored in a memory, the map information is then read-out from the memory, and displayed together with the current location of a vehicle, thereby guiding the vehicle to a predetermined destination.
In general, display of the travel locus information of the vehicle in which the on-vehicle navigation apparatus is mounted is performed on the basis of the information of current location of the vehicle for every certain travel distance or every certain running time of the vehicle.
Since the travel locus of the vehicle is a collection of discrete positional data, the shorter the interval between discrete positions, the finer the locus pattern drawn by the discrete positions. However, a larger memory capacity will be required to store the positional data. Conversely, the longer the interval between pieces of such positional data, the less amount of the positional data should be stored, thus requiring a smaller memory capacity. However, the locus pattern will become rougher with respect to map information.
With the method of collecting locus data on the basis of positional data, that is, information of the vehicle's location at every predetermined travel distance for displaying the locus data, if the interval of collection of the locus data is set at a short value, unnecessary locus data will have to be stored in a memory also in a monotonous running condition when the vehicle drives on a relatively straight street, such as an expressway. If the interval of collection of the locus data is set at a long value, the locus data will be inaccurate for a map when the vehicle drives through an area that includes intricate roads, such as town roads.
With the method of collecting locus data at every predetermined running time for displaying the locus data, if the time interval of collection of the locus data is set to be short, unnecessary locus data will have to be stored during low-speed driving. If, on the other hand, the time interval is set to be long, the locus data becomes sparse and very dispersed in terms of location, as compared with the actual locus of the moving vehicle will be acquired during high-speed driving. It is not therefore possible to provide a user with accurate locus information.